PROJECT SUMMARY/ABSTRACT There is a critical need to develop new strategies to pharmacologically manipulate key receptors expressed by podocytes, a type of extravascular glomerular cell, to understand the consequences of podocyte-receptor signaling biology and potentially deliver safe and effective pharmaceuticals to cells in the urinary space. The overall objective of this proposal is to investigate the utility of in vivo protease activated receptor (PAR) antagonism for treatment of nephrotic syndrome. The central hypothesis is that antagonism of podocyte- expressed PARs will improve podocyte survival and proteinuria in experimental nephrotic syndrome. There are significant challenges to the development of clinically viable PAR antagonists. Thus, we will investigate the ability of a novel class of `nano' antibodies, derived from camelid species, which are known to cross the glomerular filtration barrier for their ability to antagonize PAR-signaling. Using established podocyte cell culture lines, nephrotic syndrome animal models, PAR-signaling assays, and conventional small molecule PAR inhibitors, we will examine the consequences of PAR antagonism on podocyte survival and proteinuria. A novel, rapid flow cytometry approach to determining in situ podocyte survival will be validated against conventional methods. This application is directly responsive to the NIDDK Limited Competition R03 program for career development awardees; PAR-16-148. Thus, completion of the proposed research is expected to facilitate the development of unique, innovative research resources (nanobodies and flow cytometry techniques) that will accelerate the career progression of a successful K08 career development awardee toward the independent phase of his physician-scientist career. The PI is committed to applied molecular hemostasis research in the field of glomerular diseases and will thus leverage these resources to successfully compete for R01 funding to systematically analyze coagulation signaling in glomerular disease.